In recent years, solar power generation has been widely used as clean energy serving as a substitute for oil-based energy having many problems such as resource depletion and the emission of greenhouse gases. Patent document 1 discloses a method to enhance energy conversion efficiency by using silicon nitride film for an antireflection film of a silicon solar battery. Previously, in plasma CVD processing to forma silicon nitride film, a deposition process has been done under reduced pressure of 10−2 to several Torr in order to create stable plasma. Therefore, production cost reduction has been difficult because an expensive equipment and pressure reduction process in a deposition chamber are necessary. For more widespread use of solar power generation, it has been desired to develop a CVD apparatus and a production method to produce solar battery at lower cost.
Patent document 2 discloses a technology to produce a thin film by atmospheric CVD. FIG. 12 shows a cross-sectional diagram of an existing atmospheric CVD apparatus disclosed in patent document 2. In general, it is known that stable plasma state cannot be kept under atmospheric pressure when most gases are used except specific gases such as helium, and the plasma state instantly moves into an arc discharge state. In a CVD apparatus as illustrated in FIG. 12, a pair of electrodes 114 and 115 are placed facing each other in a chamber 111. And material gases are introduced from gas inlets 111 and plasma 118 is generated via solid dielectric members 116, 117 by applying electric field on electrodes 114, 115. Then a thin film 120 is formed on a substrate 121 by the plasma 118 being sprayed from a supply opening 119. Stable glow discharge plasma can be generated regardless of the difference of gas by applying electric field of the electrode via solid dielectric body. A method to form a nitride film is described in embodiment 3 of Patent Document 2. In this method, plasma is generated by introducing a mixture gas of silane gas and ammonia gas diluted by argon gas into a container 111. However, silicon plasma and nitrogen plasma do not react on the substrate but mainly react in the container according to this method. Therefore almost no nitride film can be formed on the substrate.
In Patent Document 3, a technology to produce thin film by atmospheric CVD is also disclosed. The deposition method disclosed in Patent Document 3 is film deposition in discharged space, while the deposition method disclosed in Patent Document 2 is film deposition by plasma spray. Accordingly, a nitride film deposition on the substrate becomes possible, but a difference of film deposition rate between regions around gas inlet and gas outlet becomes notable. This has lowered the film deposition uniformity when several different gases are introduced in those cases such as a nitride film deposition. And a substrate is subject to damage from plasma because the substrate is placed in a discharged space.